Systems and methods for partitioning video blocks for video coding

ABSTRACT

A video coding device may be configured to perform video coding according to one or more of the techniques described herein. In one example, a method of partitioning video data for video coding, comprises receiving a video block including sample values, and partitioning the sample values according to the following set of partitioning modes: quadtree, horizontal or vertical symmetric binary tree, horizontal or vertical asymmetric binary tree, and horizontal or vertical triple tree.

TECHNICAL FIELD

This disclosure relates to video coding and more particularly totechniques for partitioning a picture of video data.

BACKGROUND ART

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, laptop or desktop computers,tablet computers, digital recording devices, digital media players,video gaming devices, cellular telephones, including so-calledsmartphones, medical imaging devices, and the like. Digital video may becoded according to a video coding standard. Video coding standards mayincorporate video compression techniques. Examples of video codingstandards include ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known asISO/IEC MPEG-4 AVC) and High-Efficiency Video Coding (HEVC). HEVC isdescribed in High Efficiency Video Coding (HEVC), Rec. ITU-T H.265,December 2016, which is incorporated by reference, and referred toherein as ITU-T H.265. Extensions and improvements for ITU-T H.265 arecurrently being considered for the development of next generation videocoding standards. For example, the ITU-T Video Coding Experts Group(VCEG) and ISO/IEC (Moving Picture Experts Group (MPEG) (collectivelyreferred to as the Joint Video Exploration Team (JVET)) are studying thepotential need for standardization of future video coding technologywith a compression capability that significantly exceeds that of thecurrent HEVC standard. The Joint Exploration Model 7 (JEM 7), AlgorithmDescription of Joint Exploration Test Model 7 (JEM 7), ISO/IECJTC1/SC29/WG11 Document: JVET-G1001, July 2017, Torino, IT, which isincorporated by reference herein, describes the coding features that areunder coordinated test model study by the JVET as potentially enhancingvideo coding technology beyond the capabilities of ITU-T H.265. Itshould be noted that the coding features of JEM 7 are implemented in JEMreference software. As used herein, the term JEM may collectively referto algorithms included in JEM 7 and implementations of JEM referencesoftware.

Video compression techniques enable data requirements for storing andtransmitting video data to be reduced. Video compression techniques mayreduce data requirements by exploiting the inherent redundancies in avideo sequence. Video compression techniques may sub-divide a videosequence into successively smaller portions (i.e., groups of frameswithin a video sequence, a frame within a group of frames, slices withina frame, coding tree units (e.g., macroblocks) within a slice, codingblocks within a coding tree unit, etc.). Intra prediction codingtechniques (e.g., intra-picture (spatial)) and inter predictiontechniques (i.e., inter-picture (temporal)) may be used to generatedifference values between a unit of video data to be coded and areference unit of video data. The difference values may be referred toas residual data. Residual data may be coded as quantized transformcoefficients. Syntax elements may relate residual data and a referencecoding unit (e.g., intra-prediction mode indices, motion vectors, andblock vectors). Residual data and syntax elements may be entropy coded.Entropy encoded residual data and syntax elements may be included in acompliant bitstream.

SUMMARY OF INVENTION

In one example, a method of partitioning video data for video coding,comprises receiving a video block including sample values, andpartitioning the sample values according to the following set ofpartitioning modes: quadtree, horizontal or vertical symmetric binarytree, horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree.

In one example, a method of reconstructing video data comprisesreceiving signaling corresponding to a partitioning for a coded videoblock, where sample values of the video block are partitioned accordingto the following set of partitioning modes: quadtree, horizontal orvertical symmetric binary tree, horizontal or vertical asymmetric binarytree, and horizontal or vertical triple tree, and reconstructing videodata based on the partitioning for the coded video block.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example of a group ofpictures coded according to a quad tree binary tree partitioning inaccordance with one or more techniques of this disclosure.

FIG. 2 is a conceptual diagram illustrating an example of a quad treebinary tree in accordance with one or more techniques of thisdisclosure.

FIG. 3 is a conceptual diagram illustrating video component quad treebinary tree partitioning in accordance with one or more techniques ofthis disclosure.

FIG. 4 is a conceptual diagram illustrating an example of a videocomponent sampling format in accordance with one or more techniques ofthis disclosure.

FIG. 5 is a conceptual diagram illustrating possible coding structuresfor a block of video data according to one or more techniques of thisdisclosure.

FIG. 6A is a conceptual diagram illustrating an example of coding ablock of video data in accordance with one or more techniques of thisdisclosure.

FIG. 6B is a conceptual diagram illustrating an example of coding ablock of video data in accordance with one or more techniques of thisdisclosure.

FIG. 7 is a conceptual diagram illustrating partitioning in accordancewith one or more techniques of this disclosure.

FIG. 8 is a block diagram illustrating an example of a system that maybe configured to encode and decode video data according to one or moretechniques of this disclosure.

FIG. 9 is a block diagram illustrating an example of a video encoderthat may be configured to encode video data according to one or moretechniques of this disclosure.

FIG. 10 is a block diagram illustrating an example of a video decoderthat may be configured to decode video data according to one or moretechniques of this disclosure.

DESCRIPTION OF EMBODIMENTS

In general, this disclosure describes various techniques for codingvideo data. In particular, this disclosure describes techniques forpartitioning a picture of video data. It should be noted that althoughtechniques of this disclosure are described with respect to ITU-T H.264,ITU-T H.265, and JEM, the techniques of this disclosure are generallyapplicable to video coding. For example, the coding techniques describedherein may be incorporated into video coding systems, (including videocoding systems based on future video coding standards) including blockstructures, intra prediction techniques, inter prediction techniques,transform techniques, filtering techniques, and/or entropy codingtechniques other than those included in ITU-T H.265 and JEM. Thus,reference to ITU-T H.264, ITU-T H.265, and/or JEM is for descriptivepurposes and should not be construed to limit the scope of thetechniques described herein. Further, it should be noted thatincorporation by reference of documents herein is for descriptivepurposes and should not be construed to limit or create ambiguity withrespect to terms used herein. For example, in the case where anincorporated reference provides a different definition of a term thananother incorporated reference and/or as the term is used herein, theterm should be interpreted in a manner that broadly includes eachrespective definition and/or in a manner that includes each of theparticular definitions in the alternative.

In one example, a device for partitioning video data for video codingcomprises one or more processors configured to receive a video blockincluding sample values, and partition the sample values according tothe following set of partitioning modes: quadtree, horizontal orvertical symmetric binary tree, horizontal or vertical asymmetric binarytree, and horizontal or vertical triple tree.

In one example, a non-transitory computer-readable storage mediumcomprises instructions stored thereon that, when executed, cause one ormore processors of a device receive a video block including samplevalues, and partition the sample values according to the following setof partitioning modes: quadtree, horizontal or vertical symmetric binarytree, horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree.

In one example, an apparatus comprises means for receiving a video blockincluding sample values, and means for partitioning the sample valuesaccording to the following set of partitioning modes: quadtree,horizontal or vertical symmetric binary tree, horizontal or verticalasymmetric binary tree, and horizontal or vertical triple tree.

In one example, a device for reconstructing video data comprises one ormore processors configured to receive signaling corresponding to apartitioning for a coded video block, where sample values of the videoblock are partitioned according to the following set of partitioningmodes: quadtree, horizontal or vertical symmetric binary tree,horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree, and reconstruct video data based on thepartitioning for the coded video block.

In one example, a non-transitory computer-readable storage mediumcomprises instructions stored thereon that, when executed, cause one ormore processors of a device to receive signaling corresponding to apartitioning for a coded video block, where sample values of the videoblock are partitioned according to the following set of partitioningmodes: quadtree, horizontal or vertical symmetric binary tree,horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree, and reconstruct video data based on thepartitioning for the coded video block.

In one example, an apparatus comprises means for receiving signalingcorresponding to a partitioning for a coded video block, where samplevalues of the video block are partitioned according to the following setof partitioning modes: quadtree, horizontal or vertical symmetric binarytree, horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree, and means for reconstructing video data based onthe partitioning for the coded video block.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

Video content typically includes video sequences comprised of a seriesof frames (or pictures). A series of frames may also be referred to as agroup of pictures (GOP). Each video frame or picture may include aplurality of slices or tiles, where a slice or tile includes a pluralityof video blocks. As used herein, the term video block may generallyrefer to an area of a picture or may more specifically refer to thelargest array of sample values that may be predictively coded,sub-divisions thereof, and/or corresponding structures. Further, theterm current video block may refer to an area of a picture being encodedor decoded. A video block may be defined as an array of sample valuesthat may be predictively coded. It should be noted that in some casespixels values may be described as including sample values for respectivecomponents of video data, which may also be referred to as colorcomponents, (e.g., luma (Y) and chroma (Cb and Cr) components or red,green, and blue components). It should be noted that in some cases, theterms pixel values and sample values are used interchangeably. Videoblocks may be ordered within a picture according to a scan pattern(e.g., a raster scan). A video encoder may perform predictive encodingon video blocks and sub-divisions thereof. Video blocks andsub-divisions thereof may be referred to as nodes.

ITU-T H.264 specifies a macroblock including 16×16 luma samples. Thatis, in ITU-T H.264, a picture is segmented into macroblocks. ITU-T H.265specifies an analogous Coding Tree Unit (CTU) structure. In ITU-T H.265,pictures are segmented into CTUs. In ITU-T H.265, for a picture, a CTUsize may be set as including 16×16, 32×32, or 64×64 luma samples. InITU-T H.265, a CTU is composed of respective Coding Tree Blocks (CTB)for each component of video data (e.g., luma (Y) and chroma (Cb and Cr).Further, in ITU-T H.265, a CTU may be partitioned according to aquadtree (QT) partitioning structure, which results in the CTBs of theCTU being partitioned into Coding Blocks (CB). That is, in ITU-T H.265,a CTU may be partitioned into quadtree leaf nodes. According to ITU-TH.265, one luma CB together with two corresponding chroma CBs andassociated syntax elements are referred to as a coding unit (CU). InITU-T H.265, a minimum allowed size of a CB may be signaled. In ITU-TH.265, the smallest minimum allowed size of a luma CB is 8×8 lumasamples. In ITU-T H.265, the decision to code a picture area using intraprediction or inter prediction is made at the CU level.

In ITU-T H.265, a CU is associated with a prediction unit (PU) structurehaving its root at the CU. In ITU-T H.265, PU structures allow luma andchroma CBs to be split for purposes of generating correspondingreference samples. That is, in ITU-T H.265, luma and chroma CBs may besplit into respect luma and chroma prediction blocks (PBs), where a PBincludes a block of sample values for which the same prediction isapplied. In ITU-T H.265, a CB may be partitioned into 1, 2, or 4 PBs.ITU-T H.265 supports PB sizes from 64×64 samples down to 4×4 samples. InITU-T H.265, square PBs are supported for intra prediction, where a CBmay form the PB or the CB may be split into four square PBs (i.e., intraprediction PB types include M×M or M/2×M/2, where M is the height andwidth of the square CB). In ITU-T H.265, in addition to the square PBs,rectangular PBs are supported for inter prediction, where a CB may byhalved vertically or horizontally to form PBs (i.e., inter prediction PBtypes include M×M, M/2×M/2, M/2×M, or M×M/2). Further, it should benoted that in ITU-T H.265, for inter prediction, four asymmetric PBpartitions are supported, where the CB is partitioned into two PBs atone quarter of the height (at the top or the bottom) or width (at theleft or the right) of the CB (i.e., asymmetric partitions include M/4×Mleft, M/4×M right, M×M/4 top, and M×M/4 bottom). Intra prediction data(e.g., intra prediction mode syntax elements) or inter prediction data(e.g., motion data syntax elements) corresponding to a PB is used toproduce reference and/or predicted sample values for the PB.

JEM specifies a CTU having a maximum size of 256×256 luma samples. JEMspecifies a quadtree plus binary tree (QTBT) block structure. In JEM,the QTBT structure enables quadtree leaf nodes to be further partitionedby a binary tree (BT) structure. That is, in JEM, the binary treestructure enables quadtree leaf nodes to be recursively dividedvertically or horizontally. FIG. 1 illustrates an example of a CTU(e.g., a CTU having a size of 256×256 luma samples) being partitionedinto quadtree leaf nodes and quadtree leaf nodes being furtherpartitioned according to a binary tree. That is, in FIG. 1 dashed linesindicate additional binary tree partitions in a quadtree. Thus, thebinary tree structure in JEM enables square and rectangular leaf nodes,where each leaf node includes a CB. As illustrated in FIG. 1, a pictureincluded in a GOP may include slices, where each slice includes asequence of CTUs and each CTU may be partitioned according to a QTBTstructure. FIG. 1 illustrates an example of QTBT partitioning for oneCTU included in a slice. FIG. 2 is a conceptual diagram illustrating anexample of a QTBT corresponding to the example QTBT partitionillustrated in FIG. 1.

In JEM, a QTBT is signaled by signaling QT split flag and BT split modesyntax elements. When a QT split flag has a value of 1, a QT split isindicated. When a QT split flag has a value of 0, a BT split mode syntaxelement is signaled. When a BT split mode syntax element has a value of0 (i.e., BT split mode coding tree=0), no binary splitting is indicated.When a BT split mode syntax element has a value of 3 (i.e., BT splitmode coding tree=11), a vertical split mode is indicated. When a BTsplit mode syntax element has a value of 2 (i.e., BT split mode codingtree=10), a horizontal split mode is indicated. Further, BT splittingmay be performed until a maximum BT depth is reached. Thus, according toJEM, the QTBT illustrated in FIG. 2 may be signaled based on thepseudo-syntax provided in Table 1:

TABLE 1 QT flag = 1; //Depth 0 syntax  QT flag = 1; //Depth 1 syntax  QTflag = 0, BT split = 0; //Depth 2 syntax  QT flag = 0, BT split = 10;//Depth 2 syntax   BT split = 0; //Depth 3 syntax   BT split = 0;//Depth 3 syntax  QT flag = 0, BT split = 0; //Depth 2 syntax  QT flag =0, BT split = 11; //Depth 2 syntax   BT split = 0; //Depth 3 syntax   BTsplit = 0; //Depth 3 syntax  QT flag = 0; BT split = 11; //Depth 1syntax  BT split = 0; //Depth 2 syntax  BT split = 11; //Depth 2 syntax  BT split = 0; //Depth 3 syntax   BT split = 0; //Depth 3 syntax  QTflag = 0; BT split = 10; //Depth 1 syntax  BT split = 0; //Depth 2syntax  BT split = 0; //Depth 2 syntax  QT flag = 1; //Depth 1 syntax QT flag = 0, BT split = 0; //Depth 2 syntax  QT flag = 1; //Depth 2syntax   QT flag = 0, BT split = 0; //Depth 3 syntax   QT flag = 0, BTsplit = 0; //Depth 3 syntax   QT flag = 0, BT split = 0; //Depth 3syntax   QT flag = 0, BT split = 0; //Depth 3 syntax  QT flag = 0, BTsplit = 0; //Depth 2 syntax  QT flag = 0, BT split = 0. //Depth 2 syntaxAs illustrated in FIG. 2 and Table 1, QT split flag syntax elements andBT split mode syntax elements are associated with a depth, where a depthof zero corresponds to a root of a QTBT and higher value depthscorrespond to subsequent depths beyond the root. Further, in JEM, lumaand chroma components may have separate QTBT partitions. That is, in JEMluma and chroma components may be partitioned independently by signalingrespective QTBTs. FIG. 3 illustrates an example of a CTU beingpartitioned according to a QTBT for a luma component and an independentQTBT for chroma components. As illustrated in FIG. 3, when independentQTBTs are used for partitioning a CTU, CBs of the luma component are notrequired to and do not necessarily align with CBs of chroma components.Currently, in JEM independent QTBT structures are enabled for slicesusing intra prediction techniques. It should be noted that in somecases, values of chroma variables may need to be derived from theassociated luma variable values. In these cases, the sample position inchroma and chroma format may be used to determine the correspondingsample position in luma to determine the associated luma variable value.

Additionally, it should be noted that JEM includes the followingparameters for signaling of a QTBT tree:

-   -   CTU size: the root node size of a quadtree (e.g., 256×256,        128×128, 64×64, 32×32, 16×16 luma samples);    -   MinQTSize: the minimum allowed quadtree leaf node size (e.g.,        16×16, 8×8 luma samples);    -   MaxBTSize: the maximum allowed binary tree root node size, i.e.,        the maximum size of a leaf quadtree node that may be partitioned        by binary splitting (e.g., 64×64 luma samples);    -   MaxBTDepth: the maximum allowed binary tree depth, i.e., the        lowest level at which binary splitting may occur, where the        quadtree leaf node is the root (e.g., 3);    -   MinBTSize: the minimum allowed binary tree leaf node size; i.e.,        the minimum width or height of a binary leaf node (e.g., 4 luma        samples).

It should be noted that in some examples, MinQTSize, MaxBTSize,MaxBTDepth, and/or MinBTSize may be different for the differentcomponents of video.

In JEM, CBs are used for prediction without any further partitioning.That is, in JEM, a CB may be a block of sample values on which the sameprediction is applied. Thus, a JEM QTBT leaf node may be analogous a PBin ITU-T H.265.

A video sampling format, which may also be referred to as a chromaformat, may define the number of chroma samples included in a CU withrespect to the number of luma samples included in a CU. For example, forthe 4:2:0 sampling format, the sampling rate for the luma component istwice that of the chroma components for both the horizontal and verticaldirections. As a result, for a CU formatted according to the 4:2:0format, the width and height of an array of samples for the lumacomponent are twice that of each array of samples for the chromacomponents. FIG. 4 is a conceptual diagram illustrating an example of acoding unit formatted according to a 4:2:0 sample format. FIG. 4illustrates the relative position of chroma samples with respect to lumasamples within a CU. As described above, a CU is typically definedaccording to the number of horizontal and vertical luma samples. Thus,as illustrated in FIG. 4, a 16×16 CU formatted according to the 4:2:0sample format includes 16×16 samples of luma components and 8×8 samplesfor each chroma component. Further, in the example illustrated in FIG.4, the relative position of chroma samples with respect to luma samplesfor video blocks neighboring the 16×16 CU are illustrated. For a CUformatted according to the 4:2:2 format, the width of an array ofsamples for the luma component is twice that of the width of an array ofsamples for each chroma component, but the height of the array ofsamples for the luma component is equal to the height of an array ofsamples for each chroma component. Further, for a CU formatted accordingto the 4:4:4 format, an array of samples for the luma component has thesame width and height as an array of samples for each chroma component.

As described above, intra prediction data or inter prediction data isused to produce reference sample values for a block of sample values.The difference between sample values included in a current PB, oranother type of picture area structure, and associated reference samples(e.g., those generated using a prediction) may be referred to asresidual data. Residual data may include respective arrays of differencevalues corresponding to each component of video data. Residual data maybe in the pixel domain. A transform, such as, a discrete cosinetransform (DCT), a discrete sine transform (DST), an integer transform,a wavelet transform, or a conceptually similar transform, may be appliedto an array of difference values to generate transform coefficients. Itshould be noted that in ITU-T H.265, a CU is associated with a transformunit (TU) structure having its root at the CU level. That is, in ITU-TH.265, an array of difference values may be sub-divided for purposes ofgenerating transform coefficients (e.g., four 8×8 transforms may beapplied to a 16×16 array of residual values). For each component ofvideo data, such sub-divisions of difference values may be referred toas Transform Blocks (TBs). It should be noted that in ITU-T H.265, TBsare not necessarily aligned with PBs. FIG. 5 illustrates examples ofalternative PB and TB combinations that may be used for coding aparticular CB. Further, it should be noted that in ITU-T H.265, TBs mayhave the following sizes 4×4, 8×8, 16×16, and 32×32.

It should be noted that in JEM, residual values corresponding to a CBare used to generate transform coefficients without furtherpartitioning. That is, in JEM a QTBT leaf node may be analogous to botha PB and a TB in ITU-T H.265. It should be noted that in JEM, a coretransform and a subsequent secondary transforms may be applied (in thevideo encoder) to generate transform coefficients. For a video decoder,the order of transforms is reversed. Further, in JEM, whether asecondary transform is applied to generate transform coefficients may bedependent on a prediction mode.

A quantization process may be performed on transform coefficients.Quantization essentially scales transform coefficients in order to varythe amount of data required to represent a group of transformcoefficients. Quantization may include division of transformcoefficients by a quantization scaling factor and any associatedrounding functions (e.g., rounding to the nearest integer). Quantizedtransform coefficients may be referred to as coefficient level values.Inverse quantization (or “dequantization”) may include multiplication ofcoefficient level values by the quantization scaling factor. It shouldbe noted that as used herein the term quantization process in someinstances may refer to division by a scaling factor to generate levelvalues and multiplication by a scaling factor to recover transformcoefficients in some instances. That is, a quantization process mayrefer to quantization in some cases and inverse quantization in somecases.

FIGS. 6A-6B are conceptual diagrams illustrating examples of coding ablock of video data. As illustrated in FIG. 6A, a current block of videodata (e.g., a CB corresponding to a video component) is encoded bygenerating a residual by subtracting a set of prediction values from thecurrent block of video data, performing a transformation on theresidual, and quantizing the transform coefficients to generate levelvalues. As illustrated in FIG. 6B, the current block of video data isdecoded by performing inverse quantization on level values, performingan inverse transform, and adding a set of prediction values to theresulting residual. It should be noted that in the examples in FIGS.6A-6B, the sample values of the reconstructed block differs from thesample values of the current video block that is encoded. In thismanner, coding may said to be lossy. However, the difference in samplevalues may be considered acceptable or imperceptible to a viewer of thereconstructed video. Further, as illustrated in FIGS. 6A-6B, scaling isperformed using an array of scaling factors.

As illustrated in FIG. 6A, quantized transform coefficients are codedinto a bitstream. Quantized transform coefficients and syntax elements(e.g., syntax elements indicating a coding structure for a video block)may be entropy coded according to an entropy coding technique. Examplesof entropy coding techniques include content adaptive variable lengthcoding (CAVLC), context adaptive binary arithmetic coding (CABAC),probability interval partitioning entropy coding (PIPE), and the like.Entropy encoded quantized transform coefficients and correspondingentropy encoded syntax elements may form a compliant bitstream that canbe used to reproduce video data at a video decoder. An entropy codingprocess may include performing a binarization on syntax elements.Binarization refers to the process of converting a value of a syntaxvalue into a series of one or more bits. These bits may be referred toas “bins.” Binarization is a lossless process and may include one or acombination of the following coding techniques: fixed length coding,unary coding, truncated unary coding, truncated Rice coding, Golombcoding, k-th order exponential Golomb coding, and Golomb-Rice coding.For example, binarization may include representing the integer value of5 for a syntax element as 00000101 using an 8-bit fixed lengthbinarization technique or representing the integer value of 5 as 11110using a unary coding binarization technique. As used herein each of theterms fixed length coding, unary coding, truncated unary coding,truncated Rice coding, Golomb coding, k-th order exponential Golombcoding, and Golomb-Rice coding may refer to general implementations ofthese techniques and/or more specific implementations of these codingtechniques. For example, a Golomb-Rice coding implementation may bespecifically defined according to a video coding standard, for example,ITU-T H.265. An entropy coding process further includes coding binvalues using lossless data compression algorithms. In the example of aCABAC, for a particular bin, a context model may be selected from a setof available context models associated with the bin. In some examples, acontext model may be selected based on a previous bin and/or values ofprevious syntax elements. A context model may identify the probabilityof a bin having a particular value. For instance, a context model mayindicate a 0.7 probability of coding a 0-valued bin and a 0.3probability of coding a 1-valued bin. It should be noted that in somecases the probability of coding a 0-valued bin and probability of codinga 1-valued bin may not sum to 1. After selecting an available contextmodel, a CABAC entropy encoder may arithmetically code a bin based onthe identified context model. The context model may be updated based onthe value of a coded bin. The context model may be updated based on anassociated variable stored with the context, e.g., adaptation windowsize, number of bins coded using the context. It should be noted, thataccording to ITU-T H.265, a CABAC entropy encoder may be implemented,such that some syntax elements may be entropy encoded using arithmeticencoding without the usage of an explicitly assigned context model, suchcoding may be referred to as bypass coding.

As described above, intra prediction data or inter prediction data mayassociate an area of a picture (e.g., a PB or a CB) with correspondingreference samples. For intra prediction coding, an intra prediction modemay specify the location of reference samples within a picture. In ITU-TH.265, defined possible intra prediction modes include a planar (i.e.,surface fitting) prediction mode (predMode: 0), a DC (i.e., flat overallaveraging) prediction mode (predMode: 1), and 33 angular predictionmodes (predMode: 2-34). In JEM, defined possible intra-prediction modesinclude a planar prediction mode (predMode: 0), a DC prediction mode(predMode: 1), and 65 angular prediction modes (predMode: 2-66). Itshould be noted that planar and DC prediction modes may be referred toas non-directional prediction modes and that angular prediction modesmay be referred to as directional prediction modes. It should be notedthat the techniques described herein may be generally applicableregardless of the number of defined possible prediction modes.

For inter prediction coding, a motion vector (MV) identifies referencesamples in a picture other than the picture of a video block to be codedand thereby exploits temporal redundancy in video. For example, acurrent video block may be predicted from reference block(s) located inpreviously coded frame(s) and a motion vector may be used to indicatethe location of the reference block. A motion vector and associated datamay describe, for example, a horizontal component of the motion vector,a vertical component of the motion vector, a resolution for the motionvector (e.g., one-quarter pixel precision, one-half pixel precision,one-pixel precision, two-pixel precision, four-pixel precision), aprediction direction and/or a reference picture index value. Further, acoding standard, such as, for example ITU-T H.265, may support motionvector prediction. Motion vector prediction enables a motion vector tobe specified using motion vectors of neighboring blocks. Examples ofmotion vector prediction include advanced motion vector prediction(AMVP), temporal motion vector prediction (TMVP), so-called “merge”mode, and “skip” and “direct” motion inference. Further, JEM supportsadvanced temporal motion vector prediction (ATMVP) and Spatial-temporalmotion vector prediction (STMVP).

As described above, in JEM, a QTBT leaf node, which allows for arbitraryrectangular CBs, may be analogous to both a PB and a TB in ITU-T H.265.Thus, is some cases, JEM may provide less flexibility with respect topossible PB and TB structures than as provided in ITU-T H.265. Further,in ITU-T H.265, only square TBs are allowed and only square PBs areallowed for intra prediction. Thus, some processes in ITU-T H.265 aredefined based on the assumption that an array of sample values input tothe process must be square and as such, some processes in ITU-T H.265may not provide adequate support for coding arbitrary rectangular videoblocks. Further, QTBT partitioning and associated signaling as definedin JEM may be less than ideal.

As described above, ITU-T H.265 supports four asymmetric PB partitionsfor inter prediction. Further, it should be noted that with respect toJEM, techniques have been proposed for partitioning CUs according toasymmetric binary tree partitioning. F. Le Leannec, et al., “AsymmetricCoding Units in QTBT,” 4th Meeting: Chengdu, CN, 15-21 Oct. 2016, Doc.JVET-D0064 (hereinafter “Le Leannec”), describes where in addition tothe symmetric vertical and horizontal BT split modes, four additionalasymmetric BT split modes are defined. In Le Leannec, the fouradditionally defined BT split modes for a CU include: horizontalpartitioning at one quarter of the height (at the top for one mode or atthe bottom for one mode) or vertical partitioning at one quarter of thewidth (at the left for one mode or the right for one mode). The fouradditionally defined BT split modes in Le Leannec are illustrated inFIG. 7 as Hor_Up, Hor_Down, Ver_Left, and Ver_Right. Table 2 provides asummary of the bin coding tree signaling used in Le Leannec forsignaling possible partitions. It should be noted that in some examples,binary split modes that do not partition a block into equal halves maybe referred to as asymmetric binary tree (ABT) partitions.

TABLE 2 Bin Coding Tree Bin₀ Bin₁ Bin₂ Bin₃ Bin₄ Partition Type 1 N/AN/A N/A N/A Quad Tree Split 0 0 N/A N/A N/A Leaf Node 0 1 0 0 N/AHorizontal Symmetric Binary Tree 0 1 0 1 0 Horizontal 1/4 of blockdimension top (Hor_Up) 0 1 0 1 1 Horizontal 1/4 of block dimensionbottom (Hor_Down) 0 1 1 0 N/A Vertical Symmetric Binary Tree 0 1 1 1 0Vertical 1/4 of block dimension left (Ver_Left) 0 1 1 1 1 Vertical 1/4of block dimension right (Ver_Right)

Li, et al., “Multi-Type-Tree,” 4th Meeting: Chengdu, CN, 15-21 Oct.2016, Doc. JVET-D0117r1 (hereinafter “Li”), describes an example wherein addition to the symmetric vertical and horizontal BT split modes, twoadditional triple tree (TT) split modes are defined. It should be notedthat in some cases, partitioning a node into three blocks about adirection may be referring to as triple tree (TT) partitioning. In Li,the two additionally defined TT split modes for a node include: (1)horizontal TT partitioning at one quarter of the height from the topedge and the bottom edge of a node; and (2) vertical TT partitioning atone quarter of the width from the left edge and the right edge of anode. The two additionally defined TT split modes in Li are illustratedin FIG. 7 as Vertical TT and Horizontal TT. Table 3 provides a summaryof the bin coding tree signaling used in Li for signaling possiblepartitions.

TABLE 3 Bin Coding Tree Bin₀ Bin₁ Bin₂ Bin₃ Partition Type 1 N/A N/A N/AQuad Tree Split 0 0 N/A N/A Leaf Node 0 1 0 0 Horizontal SymmetricBinary Tree 0 1 0 1 Horizontal Triple Tree at 1/4 of block dimension.(Horizontal TT) 0 1 1 0 Vertical Symmetric Binary Tree 0 1 1 1 VerticalTriple Tree at 1/4 of block dimension (Vertical TT)

The techniques described in Le Leannec and Li may be less than ideal.For example, the techniques described in Le Leannec and Li may notprovide sufficient flexibility for partitioning images included detailedfeatures.

FIG. 8 is a block diagram illustrating an example of a system that maybe configured to code (i.e., encode and/or decode) video data accordingto one or more techniques of this disclosure. System 100 represents anexample of a system that may perform video coding using partitioningtechniques described according to one or more techniques of thisdisclosure. As illustrated in FIG. 8, system 100 includes source device102, communications medium 110, and destination device 120. In theexample illustrated in FIG. 8, source device 102 may include any deviceconfigured to encode video data and transmit encoded video data tocommunications medium 110. Destination device 120 may include any deviceconfigured to receive encoded video data via communications medium 110and to decode encoded video data. Source device 102 and/or destinationdevice 120 may include computing devices equipped for wired and/orwireless communications and may include set top boxes, digital videorecorders, televisions, desktop, laptop, or tablet computers, gamingconsoles, mobile devices, including, for example, “smart” phones,cellular telephones, personal gaming devices, and medical imaginingdevices.

Communications medium 110 may include any combination of wireless andwired communication media, and/or storage devices. Communications medium110 may include coaxial cables, fiber optic cables, twisted pair cables,wireless transmitters and receivers, routers, switches, repeaters, basestations, or any other equipment that may be useful to facilitatecommunications between various devices and sites. Communications medium110 may include one or more networks. For example, communications medium110 may include a network configured to enable access to the World WideWeb, for example, the Internet. A network may operate according to acombination of one or more telecommunication protocols.Telecommunications protocols may include proprietary aspects and/or mayinclude standardized telecommunication protocols. Examples ofstandardized telecommunications protocols include Digital VideoBroadcasting (DVB) standards, Advanced Television Systems Committee(ATSC) standards, Integrated Services Digital Broadcasting (ISDB)standards, Data Over Cable Service Interface Specification (DOCSIS)standards, Global System Mobile Communications (GSM) standards, codedivision multiple access (CDMA) standards, 3rd Generation PartnershipProject (3GPP) standards, European Telecommunications StandardsInstitute (ETSI) standards, Internet Protocol (IP) standards, WirelessApplication Protocol (WAP) standards, and Institute of Electrical andElectronics Engineers (IEEE) standards.

Storage devices may include any type of device or storage medium capableof storing data. A storage medium may include a tangible ornon-transitory computer-readable media. A computer readable medium mayinclude optical discs, flash memory, magnetic memory, or any othersuitable digital storage media. In some examples, a memory device orportions thereof may be described as non-volatile memory and in otherexamples portions of memory devices may be described as volatile memory.Examples of volatile memories may include random access memories (RAM),dynamic random access memories (DRAM), and static random access memories(SRAM). Examples of non-volatile memories may include magnetic harddiscs, optical discs, floppy discs, flash memories, or forms ofelectrically programmable memories (EPROM) or electrically erasable andprogrammable (EEPROM) memories. Storage device(s) may include memorycards (e.g., a Secure Digital (SD) memory card), internal/external harddisk drives, and/or internal/external solid state drives. Data may bestored on a storage device according to a defined file format.

Referring again to FIG. 8, source device 102 includes video source 104,video encoder 106, and interface 108. Video source 104 may include anydevice configured to capture and/or store video data. For example, videosource 104 may include a video camera and a storage device operablycoupled thereto. Video encoder 106 may include any device configured toreceive video data and generate a compliant bitstream representing thevideo data. A compliant bitstream may refer to a bitstream that a videodecoder can receive and reproduce video data therefrom. Aspects of acompliant bitstream may be defined according to a video coding standard.When generating a compliant bitstream video encoder 106 may compressvideo data. Compression may be lossy (discernible or indiscernible) orlossless. Interface 108 may include any device configured to receive acompliant video bitstream and transmit and/or store the compliant videobitstream to a communications medium. Interface 108 may include anetwork interface card, such as an Ethernet card, and may include anoptical transceiver, a radio frequency transceiver, or any other type ofdevice that can send and/or receive information. Further, interface 108may include a computer system interface that may enable a compliantvideo bitstream to be stored on a storage device. For example, interface108 may include a chipset supporting Peripheral Component Interconnect(PCI) and Peripheral Component Interconnect Express (PCIe) busprotocols, proprietary bus protocols, Universal Serial Bus (USB)protocols, I²C, or any other logical and physical structure that may beused to interconnect peer devices.

Referring again to FIG. 8, destination device 120 includes interface122, video decoder 124, and display 126. Interface 122 may include anydevice configured to receive a compliant video bitstream from acommunications medium. Interface 108 may include a network interfacecard, such as an Ethernet card, and may include an optical transceiver,a radio frequency transceiver, or any other type of device that canreceive and/or send information. Further, interface 122 may include acomputer system interface enabling a compliant video bitstream to beretrieved from a storage device. For example, interface 122 may includea chipset supporting PCI and PCIe bus protocols, proprietary busprotocols, USB protocols, I²C, or any other logical and physicalstructure that may be used to interconnect peer devices. Video decoder124 may include any device configured to receive a compliant bitstreamand/or acceptable variations thereof and reproduce video data therefrom.Display 126 may include any device configured to display video data.Display 126 may comprise one of a variety of display devices such as aliquid crystal display (LCD), a plasma display, an organic lightemitting diode (OLED) display, or another type of display. Display 126may include a High Definition display or an Ultra High Definitiondisplay. It should be noted that although in the example illustrated inFIG. 8, video decoder 124 is described as outputting data to display126, video decoder 124 may be configured to output video data to varioustypes of devices and/or sub-components thereof. For example, videodecoder 124 may be configured to output video data to any communicationmedium, as described herein.

FIG. 9 is a block diagram illustrating an example of video encoder 200that may implement the techniques for encoding video data describedherein. It should be noted that although example video encoder 200 isillustrated as having distinct functional blocks, such an illustrationis for descriptive purposes and does not limit video encoder 200 and/orsub-components thereof to a particular hardware or softwarearchitecture. Functions of video encoder 200 may be realized using anycombination of hardware, firmware, and/or software implementations. Inone example, video encoder 200 may be configured to encode video dataaccording to the techniques described herein. Video encoder 200 mayperform intra prediction coding and inter prediction coding of pictureareas, and, as such, may be referred to as a hybrid video encoder. Inthe example illustrated in FIG. 9, video encoder 200 receives sourcevideo blocks. In some examples, source video blocks may include areas ofpicture that has been divided according to a coding structure. Forexample, source video data may include macroblocks, CTUs, CBs,sub-divisions thereof, and/or another equivalent coding unit. In someexamples, video encoder 200 may be configured to perform additionalsub-divisions of source video blocks. It should be noted that sometechniques described herein may be generally applicable to video coding,regardless of how source video data is partitioned prior to and/orduring encoding. In the example illustrated in FIG. 9, video encoder 200includes summer 202, transform coefficient generator 204, coefficientquantization unit 206, inverse quantization/transform processing unit208, summer 210, intra prediction processing unit 212, inter predictionprocessing unit 214, filter unit 216, and entropy encoding unit 218.

As illustrated in FIG. 9, video encoder 200 receives source video blocksand outputs a bitstream. As described above, QTBT partitioningtechniques in JEM and proposed modification thereto may be less thanideal. According to the techniques described herein, video encoder 200may be configured to partition a video block using a combination of theQT partitioning, symmetric BT partitioning, ABT partitioning, and TTpartitioning. Table 4 illustrates an example of bin coding signalingthat may be used for signaling QT partitioning, symmetric BTpartitioning, ABT partitioning, and TT partitioning according to thetechniques described herein.

TABLE 4 Bin Coding Bin₀ Bin₁ Bin₂ Bin₃ Bin₄ Bin₅ Partition Type 1 N/AN/A N/A N/A N/A Quad 0 0 N/A N/A N/A N/A Leaf Node 0 1 0 0 N/A N/AHorizontal Triple Tree at 1/4 of block dimension. (Horizontal TT) 0 1 10 N/A N/A Vertical Triple Tree at 1/4 of block dimension. (Vertical TT)0 1 0 1 0 N/A Horizontal BT 0 1 0 1 1 0 Horizontal ABT at 1/4 from top(Hor_Up) 0 1 0 1 1 1 Horizontal ABT at 1/4 from bottom (Hor_Down) 0 1 11 0 N/A Vertical BT 0 1 1 1 1 0 Vertical ABT at 1/4 from left (Ver_Left)0 1 1 1 1 1 Vertical ABT at 1/4 from right (Ver_Right)

It should be noted that in other examples, the types of partitions andbin strings illustrated in Table 4 may be interchanged. With respect toTable 4, in one example, subsequent QT partitioning may be allowed for anode formed according to another type of partition. For example, a nodeformed from a TT partition (e.g., the central node) may be allowed to besubsequently partitioned according to a QT partitioning. In one example,BT and/or TT partitioning may be allowed for a node formed according toanother type of partition. In one example, subsequent QT, BTpartitioning, and/or TT partitioning may not be allowed for a nodeformed according to another type of partition. In some cases, whethersubsequent QT, BT, and/or TT partitioning is allowed may depend onparticular nodes of a parent partition. For example, differentpartitioning types may be allowed for the center and outer nodesresulting from a TT partitioning.

With respect to Table 4, parameters QTDepth, BTDepth, ABTDepth, TTDepth,and TotalDepth may be defined as follows:

-   -   QTDepth: the current QT depth is equal to the number of times QT        partition has been performed starting from the root of the        partitioning tree for the CTU to the current CU. The current QT        depth will increase by one whenever a QT partition is performed,    -   BTDepth: the current BT depth is equal to the number of times        symmetric BT partitioning has been performed starting from the        root of the partitioning tree for the CTU to the current CU. The        current BT depth wilt increase by one whenever a BT partition is        performed;    -   ABTDepth: the current ABT depth is equal to the number of times        ABT partition has been performed starting from the root of the        partitioning tree for the CTU to the current CU. The current ABT        depth will increase by one whenever a ABT partition is        performed;    -   TTDepth: the current TT depth is equal to the number of times TT        partition has been performed starting from the root of the        partitioning tree for the CTU to the current CU. The current QT        depth will increase by one whenever a QT partition is performed;    -   TotalDepth: the current Total depth is equal to the sum of        QTDepth, BTDepth, ABTDepth, and TTDepth.

In one example, subsequent QT partitioning may not be allowed accordingto one or more of the following examples. In one example, a M×N block isnot allowed to be split by QT when M/2 or N/2 is odd. In some cases, Mmay be equal to N. In one example, a M×N block is not allowed to besplit by QT when M or N is equal to or smaller than minQTSize. In oneexample, a M×N block is not allowed to be split by QT when the currentQT depth is larger than or equal to a QT depth threshold value. In oneexample, a M×N block is not allowed to be split by QT when the currentQT depth is smaller than or equal to a QT depth threshold value. Itshould be noted that in some examples, QT depth threshold values mayvary from slice-to-slice.

In one example, whether subsequent QT, BT, and/or TT partitioning isallowed may depend on one or more of the following: block size,picture/slice type (e.g., intra or inter), number of samples, and/orpre-determined number minimum number of samples for allowed partitions;the minimum CU size allowed for the frame; the depths of neighboringCUs; the BT, TT and ABT depths of the current CU; the sizes of CUs inthe previous pictures; the value of a high-level flag (e.g., a flag in aslice header, or parameter set); a temporal ID of the current picture;image statistics (e.g., energy of transform coefficients, sum of squaresof coefficient levels, etc.) of neighboring CUs, and/or co-located CUsin previously coded pictures. It should be noted that image statisticsmay provide an indication of prediction quality and in some examples, itmay be useful to enable more partitioning options in regions whereprediction quality is indicated as poor.

As described above, in some examples, whether subsequent QT, BT, and/orTT partitioning is allowed may depend on particular nodes of a parentpartition. In some examples, whether a subsequent partition is allowedfor a particular node may be based on whether a resulting partition isredundant. For example, for a central node resulting from a TT verticalpartition, subsequent QT and/or BT vertical partitions may not beallowed due to the nodes resulting from the subsequent QT partitioningbeing redundant to a combination of symmetric BT partitions and thenodes resulting the subsequent BT vertical partitioning being redundantto two vertical symmetric BT partitions. Similarly, for a central noderesulting from a TT horizontal partition, subsequent QT and BThorizontal partitions may not be allowed.

It should be noted that in cases where QT, BT, and/or TT partitioningare not allowed for a node, the example bin coding signaling illustratedin Table 4 used for signaling QT partitioning, symmetric BTpartitioning, ABT partitioning, and TT partitioning may be modified.That is, the signaling may be simplified to exclude partitions that arenot allowed. Table 5 illustrates an example of bin coding signaling usedfor a node where QT partitioning is not allowed. Table 6 illustrates anexample of bin coding signaling used for a node where BT partitioning isnot allowed. Table 7 illustrates an example of bin coding signaling usedfor a node where QT and BT partitionings are not allowed.

TABLE 5 Bin Coding Bin₀ Bin₁ Bin₂ Bin₃ Bin₄ Partition Type 0 N/A N/A N/AN/A Leaf Node 1 0 0 N/A N/A Horizontal Triple Tree at 1/4 of blockdimension. (Horizontal TT) 1 1 0 N/A N/A Vertical Triple Tree at 1/4 ofblock dimension. (Vertical TT) 1 0 1 0 N/A Horizontal BT 1 0 1 1 0Horizontal ABT at 1/4 from top (Hor_Up) 1 0 1 1 1 Horizontal ABT at 1/4from bottom (Hor_Down) 1 1 1 0 N/A Vertical BT 1 1 1 1 0 Vertical ABT at1/4 from left (Ver_Left) 1 1 1 1 1 Vertical ABT at 1/4 from right(Ver_Right)

TABLE 6 Bin Coding Bin₀ Bin₁ Bin₂ Bin₃ Bin₄ Partition Type 1 N/A N/A N/AN/A Quad 0 0 N/A N/A N/A Leaf Node 0 1 0 0 N/A Horizontal Triple Tree at1/4 of block dimension. (Horizontal TT) 0 1 1 0 N/A Vertical Triple Treeat 1/4 of block dimension. (Vertical TT) 0 1 0 1 0 Horizontal ABT at 1/4from top (Hor_Up) 0 1 0 1 1 Horizontal ABT at 1/4 from bottom (Hor_Down)0 1 1 1 0 Vertical ABT at 1/4 from left (Ver_Left) 0 1 1 1 1 VerticalABT at 1/4 from right (Ver_Right)

TABLE 7 Bin Coding Bin₀ Bin₁ Bin₂ Bin₃ Partition Type 0 N/A N/A N/A LeafNode 1 0 0 N/A Horizontal Triple Tree at 1/4 of block dimension.(Horizontal TT) 1 1 0 N/A Vertical Triple Tree at 1/4 of blockdimension. (Vertical TT) 1 0 1 0 Horizontal ABT at 1/4 from top (Hor_Up)1 0 1 1 Horizontal ABT at 114 from bottom (Hor_Down) 1 1 1 0 VerticalABT at 1/4 from left (Ver_Left) 1 1 1 1 Vertical ABT at 1/4 from right(Ver_Right)

It should be noted that in some examples, for example, with respect toTable 4 and Table 5, there may be various cases where a QT split flag issignaled or not signaled. For example, in one example, a QT split flagmay be signaled after one or several BT, TT or ABT flags are signaled.In one example, a QT split flag may be signaled dependent on the currentQT depth. In one example, a QT split flag may be signaled dependent onthe current CU size. In one example, a QT split flag may be signaleddependent on the QT depths of neighboring CUs. In one example, a QTsplit flag may be signaled dependent on the minimal allowed QT width andheight, which may be indicated in a parameter set or slice header. Inone example, a QT split flag may be signaled dependent on imagestatistics of neighboring and/or co-located CUs in previously codedframes.

It should be noted that in some cases, splits may round to the nearest Nsamples. For example, a video coding implementation may require that theheight and/or width of a video block be a multiple of four. Thus, insome cases, symmetric BT splits and ABT splits may result in the samepartitioning. For example, in the case where the height of a video blockis required to be a multiple of four and the height to be split is 24,both an BT and an ABT result in two sub-blocks having a height of 12. Inone example, if the resulting split offset of a symmetric BT split isequal to that of the offset of a ABT split, video encoder 200, may onlyuse the symmetric BT split mode and the bin coding may be simplified.For example, referring to Table 4, in one example, since the BT splitand one of the ABT splits are equivalent, the following simplificationmay occur: semantically redefine Bin₄ such that a value 0 indicates asymmetric BT split and a value of 1 indicates the non-equivalent ABTsplit. It should be noted that in this case, in one example, theassociated CABAC context of Bin₄ may be unchanged. In one example, thefollowing simplification may occur, Bin₄ coding is skipped altogether.

As described above, the example bin coding signaling illustrated inTable 4 used for signaling QT partitioning, symmetric BT partitioning,ABT partitioning, and TT partitioning may be modified. For example, asdescribed above in some cases, the coding of Bin₄ may be skipped. Thus,in some cases, a video coding process need not check the value of bin(s)corresponding to a partitioning mode that is skipped. Thus, in oneexample, a video coding device may implement a process to determiningwhether or not it is necessary and/or how to check the value of binscorresponding to partitioning modes. In one example, a video codingdevice may be configured to determine whether and/or how to checkpartitioning modes based on the following process:

-   -   Define an array        bNeedCheckSplitMode[NUM_SPLIT_MODES]={eheckNoSplit,        checkQTSplit, checkBTVerSplit, checkBTHorSplit, checkTTVerSplit,        checkTTHorSplit checkVer_Left, checkHor_Up, checkVer_Right,        checkHor_Down}. The initial values of the variables at each        position in the array indicates if the corresponding split mode        is valid (1) or not (0).    -   Where the values in the bNeedCheckSplitMode may depend on        several conditions. For example, the values may depend on the        conditions described above. The values in the array        bNeedCheckSplitMode may be 0 or 1.        -   SumCheckFlags=Σ_(i=1)            ^(NUM_SPLIT_MODES−1)bNeedCheckSplitMode[i]        -   For decoding the current split mode, s,            -   Iteration k from 0 to NUM_SPLIT_MODES−1.            -   Check whether SumCheckFlags is equal to 1                -   If so, s should be the split mode with                    bNeedCheckSplitMode[s] equal to 1 and break the                    iteration.            -   Otherwise,                -   If bNeedCheckSplitMode[k] is equal to 1 then, decode                    one bin.                -    If the bin indicates split mode is equal to k then,                    s is set to k and break the iteration.                -    Otherwise, SumCheckFlags minus set                    bNeedCheckSplitMode[k] to 0 and continue the                    iteration    -   The value of s indicates the split mode.

In one example, truncated unary binarization (or its complement) may beused for signaling split modes. In one example, if only one split modeis valid, then no explicit signaling is needed in the bitstream and avideo decoder infers the corresponding split mode. In one example, aflag is included in the bitstream for each valid split mode, except thelast valid split mode. When a split mode is indicated as selected by aflag, then the flags corresponding to the remaining split modes do nothave to be signaled. A video decoder uses the flag(s) to determine theselected split mode. If all flag(s) indicate that the correspondingsplit mode is not selected, then the last split mode is inferred by avideo decoder.

In one example, video encoder 200 may be configured to test and selectthe most efficient partitioning among the partition modes illustrated inTable 4. It should be noted that the most efficient partitioning denotesa partitioning with the current minimal rate-distortion cost for acurrent CU. In one example, video encoder 200 may be configured to testthe partition modes in the following order:

-   -   NO_SPLIT partitioning with different modes    -   QT split partitioning    -   BT_HORZ split partitioning    -   BT_VERT split partitioning    -   TT_HORZ split partitioning    -   TT_VERT split partitioning    -   ABT_HORZ split partitioning    -   ABT_VERT split partitioning

In one example, when a test for a partitioning mode is finished, videoencoder 200 may check whether the most efficient partitioning includes aNO_SPLIT partition and whether the partitioning includes aQT/BB/TT/ABT/Total depth that is larger than a threshold and if thiscondition occurs, video encoder 200 may skip testing the otherpartitioning modes.

Referring again to FIG. 9, video encoder 200 may generate residual databy subtracting a predictive video block from a source video block.Summer 202 represents a component configured to perform this subtractionoperation. In one example, the subtraction of video blocks occurs in thepixel domain. Transform coefficient generator 204 applies a transform,such as a discrete cosine transform (DCT), a discrete sine transform(DST), or a conceptually similar transform, to the residual block orsub-divisions thereof (e.g., four 8×8 transforms may be applied to a16×16 array of residual values) to produce a set of residual transformcoefficients. Transform coefficient generator 204 may be configured toperform any and all combinations of the transforms included in thefamily of discrete trigonometric transforms. As described above, inITU-T H.265, TBs are restricted to the following sizes 4×4, 8×8, 16×16,and 32×32. In one example, transform coefficient generator 204 may beconfigured to perform transformations according to arrays having sizesof 4×4, 8×8, 16×16, and 32×32. In one example, transform coefficientgenerator 204 may be further configured to perform transformationsaccording to arrays having other dimensions. In particular, in somecases, it may be useful to perform transformations on rectangular arraysof difference values. In one example, transform coefficient generator204 may be configured to perform transformations according to thefollowing sizes of arrays: 2×2, 2×4N, 4M×2, and/or 4M×4N. In oneexample, a 2-dimensional (2D) M×N inverse transform may be implementedas 1-dimensional (1D) M-point inverse transform followed by a 1D N-pointinverse transform. In one example, a 2D inverse transform may beimplemented as a 1D N-point vertical transform followed by a 1D N-pointhorizontal transform. In one example, a 2D inverse transform may beimplemented as a 1D N-point horizontal transform followed by a 1DN-point vertical transform. Transform coefficient generator 204 mayoutput transform coefficients to coefficient quantization unit 206.

Coefficient quantization unit 206 may be configured to performquantization of the transform coefficients. As described above, thedegree of quantization may be modified by adjusting a quantizationparameter. Coefficient quantization unit 206 may be further configuredto determine quantization parameters and output QP data (e.g., data usedto determine a quantization group size and/or delta QP values) that maybe used by a video decoder to reconstruct a quantization parameter toperform inverse quantization during video decoding. It should be notedthat in other examples, one or more additional or alternative parametersmay be used to determine a level of quantization (e.g., scalingfactors). The techniques described herein may be generally applicable todetermining a level of quantization for transform coefficientscorresponding to a component of video data based on a level ofquantization for transform coefficients corresponding another componentof video data.

As illustrated in FIG. 9, quantized transform coefficients are output toinverse quantization/transform processing unit 208. Inversequantization/transform processing unit 208 may be configured to apply aninverse quantization and an inverse transformation to generatereconstructed residual data. As illustrated in FIG. 9, at summer 210,reconstructed residual data may be added to a predictive video block. Inthis manner, an encoded video block may be reconstructed and theresulting reconstructed video block may be used to evaluate the encodingquality for a given prediction, transformation, and/or quantization.Video encoder 200 may be configured to perform multiple coding passes(e.g., perform encoding while varying one or more of a prediction,transformation parameters, and quantization parameters). Therate-distortion of a bitstream or other system parameters may beoptimized based on evaluation of reconstructed video blocks. Further,reconstructed video blocks may be stored and used as reference forpredicting subsequent blocks.

As described above, a video block may be coded using an intraprediction. Intra prediction processing unit 212 may be configured toselect an intra prediction mode for a video block to be coded. Intraprediction processing unit 212 may be configured to evaluate a frameand/or an area thereof and determine an intra prediction mode to use toencode a current block. As illustrated in FIG. 8, intra predictionprocessing unit 212 outputs intra prediction data (e.g., syntaxelements) to entropy encoding unit 218 and transform coefficientgenerator 204. As described above, a transform performed on residualdata may be mode dependent. As described above, possible intraprediction modes may include planar prediction modes, DC predictionmodes, and angular prediction modes. Further, in some examples, aprediction for a chroma component may be inferred from an intraprediction for a luma prediction mode. Inter prediction processing unit214 may be configured to perform inter prediction coding for a currentvideo block. Inter prediction processing unit 214 may be configured toreceive source video blocks and calculate a motion vector for PUs of avideo block. A motion vector may indicate the displacement of a PU (orsimilar coding structure) of a video block within a current video framerelative to a predictive block within a reference frame. Interprediction coding may use one or more reference pictures. Further,motion prediction may be uni-predictive (use one motion vector) orbi-predictive (use two motion vectors). Inter prediction processing unit214 may be configured to select a predictive block by calculating apixel difference determined by, for example, sum of absolute difference(SAD), sum of square difference (SSD), or other difference metrics. Asdescribed above, a motion vector may be determined and specifiedaccording to motion vector prediction. Inter prediction processing unit214 may be configured to perform motion vector prediction, as describedabove. Inter prediction processing unit 214 may be configured togenerate a predictive block using the motion prediction data. Forexample, inter prediction processing unit 214 may locate a predictivevideo block within a frame buffer (not shown in FIG. 9). It should benoted that inter prediction processing unit 214 may further beconfigured to apply one or more interpolation filters to a reconstructedresidual block to calculate sub-integer pixel values for use in motionestimation. Inter prediction processing unit 214 may output motionprediction data for a calculated motion vector to entropy encoding unit218. As illustrated in FIG. 9, inter prediction processing unit 214 mayreceive reconstructed video block via filter unit 216. Filter unit 216may be configured to perform deblocking and/or Sample Adaptive Offset(SAO) filtering. Deblocking refers to the process of smoothing theboundaries of reconstructed video blocks (e.g., make boundaries lessperceptible to a viewer). SAO filtering is a non-linear amplitudemapping that may be used to improve reconstruction by adding an offsetto reconstructed video data.

Referring again to FIG. 9, entropy encoding unit 218 receives quantizedtransform coefficients and predictive syntax data (i.e., intraprediction data, motion prediction data, QP data, etc.). It should benoted that in some examples, coefficient quantization unit 206 mayperform a scan of a matrix including quantized transform coefficientsbefore the coefficients are output to entropy encoding unit 218. Inother examples, entropy encoding unit 218 may perform a scan. Entropyencoding unit 218 may be configured to perform entropy encodingaccording to one or more of the techniques described herein. Entropyencoding unit 218 may be configured to output a compliant bitstream,i.e., a bitstream that a video decoder can receive and reproduce videodata therefrom.

As described above, in the example of a CABAC, for a particular bin, acontext model may be selected from a set of available context modelsassociated with the bin and in some examples, a context model may beselected based on a previous bin and/or values of previous syntaxelements. In one example, when coding QT split for a channel, contextindex, CtxIdx for selecting a context model may be derived as follows:

-   -   CtxtIdx=0    -   If Left block's QT depth is greater than current QT depth,        CtxIdx++    -   If Top block's QT depth is greater than current QT depth,        CtxtIdx++    -   Use CtxtIdx to code QT split

In one example, when coding QT split for a channel, context index,CtxIdx for selecting a context model may be derived as follows:

-   -   CtxtIdx=0    -   If Left block's Total depth is greater than current Total depth,        CtxtIdx++    -   If Top block's Total depth is greater than current Total depth,        CtxtIdx++    -   Use CtxtIdx to code QT split

As describe above, if the offset of a symmetric BT split is equal tothat of the offset of a ABT split, video encoder 200, in some examples,may skip coding Bin₄ in Table 4. In the case where, Bin₄ and Bin₅ usedifferent contexts (e.g., ctxt0 for Bin₄ and ctxt1 for Bin₅), whencoding of Bin₄ is skipped, the context for Bin₅, uiCtxIdx, may becalculated as follows:

uiCtxIdx=uiWidth==uiHeight?0:(uiWidth>uiHeight?1:2)

-   -   where,        -   = is an “Equal to” relational operator;        -   > is a “Greater than” relational operator;        -   x?y:z If x is TRUE or not equal to 0, evaluates to the value            of y; otherwise, evaluates to the value of z: and    -   uiWidth and uiHeight are the width and height of the video block        corresponding to Bin₅

In this manner, video encoder 200 represents an example of a deviceconfigured to receive a video block including sample values andpartition the sample values according to the following set ofpartitioning modes: quadtree, horizontal or vertical symmetric binarytree, horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree.

FIG. 10 is a block diagram illustrating an example of a video decoderthat may be configured to decode video data according to one or moretechniques of this disclosure. In one example, video decoder 300 may beconfigured to reconstruct video data based on one or more of thetechniques described above. That is, video decoder 300 may operate in areciprocal manner to video encoder 200 described above. Video decoder300 may be configured to perform intra prediction decoding and interprediction decoding and, as such, may be referred to as a hybriddecoder. In the example illustrated in FIG. 10 video decoder 300includes an entropy decoding unit 302, inverse quantization unit 304,inverse transformation processing unit 306, intra prediction processingunit 308, inter prediction processing unit 310, summer 312, filter unit314, and reference buffer 316. Video decoder 300 may be configured todecode video data in a manner consistent with a video encoding system,which may implement one or more aspects of a video coding standard. Itshould be noted that although example video decoder 300 is illustratedas having distinct functional blocks, such an illustration is fordescriptive purposes and does not limit video decoder 300 and/orsub-components thereof to a particular hardware or softwarearchitecture. Functions of video decoder 300 may be realized using anycombination of hardware, firmware, and/or software implementations.

As illustrated in FIG. 10, entropy decoding unit 302 receives an entropyencoded bitstream. Entropy decoding unit 302 may be configured to decodequantized syntax elements and quantized coefficients from the bitstreamaccording to a process reciprocal to an entropy encoding process.Entropy decoding unit 302 may be configured to perform entropy decodingaccording any of the entropy coding techniques described above. Entropydecoding unit 302 may parse an encoded bitstream in a manner consistentwith a video coding standard. Video decoder 300 may be configured toparse an encoded bitstream where the encoded bitstream is generatedbased on the techniques described above. That is, for example, videodecoder 300 may be configured to determine partitioning structuresgenerated and/or signaled based on one or more of the techniquesdescribed above for purposes of reconstructing video data. For example,video decoder 300 may be configured to parse syntax elements and/orevaluate properties of video data in order to determine a partitioning.

Referring again to FIG. 10, inverse quantization unit 304 receivesquantized transform coefficients (i.e., level values) and quantizationparameter data from entropy decoding unit 302. Quantization parameterdata may include any and all combinations of delta QP values and/orquantization group size values and the like described above. Videodecoder 300 and/or inverse quantization unit 304 may be configured todetermine QP values used for inverse quantization based on valuessignaled by a video encoder and/or through video properties and/orcoding parameters. That is, inverse quantization unit 304 may operate ina reciprocal manner to coefficient quantization unit 206 describedabove. For example, inverse quantization unit 304 may be configured toinfer predetermined values (e.g., determine a sum of QT depth and BTdepth based on coding parameters), allowed quantization group sizes, andthe like, according to the techniques described above. Inversequantization unit 304 may be configured to apply an inversequantization. Inverse transform processing unit 306 may be configured toperform an inverse transformation to generate reconstructed residualdata. The techniques respectively performed by inverse quantization unit304 and inverse transform processing unit 306 may be similar totechniques performed by inverse quantization/transform processing unit208 described above. Inverse transform processing unit 306 may beconfigured to apply an inverse DCT, an inverse DST, an inverse integertransform, Non-Separable Secondary Transform (NSST), or a conceptuallysimilar inverse transform processes to the transform coefficients inorder to produce residual blocks in the pixel domain. Further, asdescribed above, whether a particular transform (or type of particulartransform) is performed may be dependent on an intra prediction mode. Asillustrated in FIG. 10, reconstructed residual data may be provided tosummer 312. Summer 312 may add reconstructed residual data to apredictive video block and generate reconstructed video data. Apredictive video block may be determined according to a predictive videotechnique (i.e., intra prediction and inter frame prediction). In oneexample, video decoder 300 and the filter unit 314 may be configured todetermine QP values and use them for post filtering (e.g., deblocking).In one example, other functional blocks of the video decoder 300 whichmake use of QP may determine QP based on received signaling and use thatfor decoding.

Intra prediction processing unit 308 may be configured to receive intraprediction syntax elements and retrieve a predictive video block fromreference buffer 316. Reference buffer 316 may include a memory deviceconfigured to store one or more frames of video data. Intra predictionsyntax elements may identify an intra prediction mode, such as the intraprediction modes described above. In one example, intra predictionprocessing unit 308 may reconstruct a video block using according to oneor more of the intra prediction coding techniques described herein.Inter prediction processing unit 310 may receive inter prediction syntaxelements and generate motion vectors to identify a prediction block inone or more reference frames stored in reference buffer 316. Interprediction processing unit 310 may produce motion compensated blocks,possibly performing interpolation based on interpolation filters.Identifiers for interpolation filters to be used for motion estimationwith sub-pixel precision may be included in the syntax elements. Interprediction processing unit 310 may use interpolation filters tocalculate interpolated values for sub-integer pixels of a referenceblock. Filter unit 314 may be configured to perform filtering onreconstructed video data. For example, filter unit 314 may be configuredto perform deblocking and/or SAO filtering, as described above withrespect to filter unit 216. Further, it should be noted that in someexamples, filter unit 314 may be configured to perform proprietarydiscretionary filter (e.g., visual enhancements). As illustrated in FIG.10, a reconstructed video block may be output by video decoder 300. Inthis manner, video decoder 300 may be configured to generatereconstructed video data according to one or more of the techniquesdescribed herein. In this manner video decoder 300 represents an exampleof a device configured to receive signaling corresponding to apartitioning for a coded video block, where sample values of the videoblock are partitioned according to the following set of partitioningmodes: quadtree, horizontal or vertical symmetric binary tree,horizontal or vertical asymmetric binary tree, and horizontal orvertical triple tree, and reconstruct video data based on thepartitioning for the coded video block.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Moreover, each functional block or various features of the base stationdevice and the terminal device used in each of the aforementionedembodiments may be implemented or executed by a circuitry, which istypically an integrated circuit or a plurality of integrated circuits.The circuitry designed to execute the functions described in the presentspecification may comprise a general-purpose processor, a digital signalprocessor (DSP), an application specific or general applicationintegrated circuit (ASIC), a field programmable gate array (FPGA), orother programmable logic devices, discrete gates or transistor logic, ora discrete hardware component, or a combination thereof. Thegeneral-purpose processor may be a microprocessor, or alternatively, theprocessor may be a conventional processor, a controller, amicrocontroller or a state machine. The general-purpose processor oreach circuit described above may be configured by a digital circuit ormay be configured by an analogue circuit. Further, when a technology ofmaking into an integrated circuit superseding integrated circuits at thepresent time appears due to advancement of a semiconductor technology,the integrated circuit by this technology is also able to be used.

Various examples have been described. These and other examples arewithin the scope of the following claims.

CROSS REFERENCE

This Nonprovisional application claims priority under 35 U.S.C. § 119 onprovisional Application No. 62/612,180 on Dec. 29, 2017, the entirecontents of which are hereby incorporated by reference.

1-10. (canceled)
 11. A method of partitioning video data for videocoding, the method comprising: determining a partitioning for a videoblock according to a set of partitioning modes which are quadtree,horizontal symmetric binary tree, vertical symmetric binary tree,horizontal triple tree, and vertical triple tree, wherein, for a centralnode resulting from a triple tree partition, subsequent quadtreepartitionings and a subsequent symmetric binary tree partitioning whichis parallel to the triple tree partition are disallowed; and signalingthe determined partitioning for the video block.
 12. The method of claim11, wherein signaling the determined partitioning for the video blockincludes when subsequent partitions are disallowed, excluding bins fromthe signaling indicating partitions that are not allowed.
 13. A methodof reconstructing video data, the method comprising: receiving signalingcorresponding to a partitioning for a coded video block, according to aset of partitioning modes which are quadtree, horizontal symmetricbinary tree, vertical symmetric binary tree, horizontal triple tree, andvertical triple tree; determining the partitioning for the coded videoblock based on the received signaling, wherein for a central noderesulting from a triple tree partition, subsequent quadtreepartitionings and a subsequent symmetric binary tree partitioning whichis parallel to the triple tree partition are disallowed; andreconstructing video data based on the determined partitioning for thecoded video block.
 14. The method of claim 13, wherein the receivedsignaling excludes bins indicating partitions that are not allowed. 15.A device for reconstructing video data, the device comprising one ormore processors configured to: receive signaling corresponding to apartitioning for a coded video block, according to a set of partitioningmodes which are quadtree, horizontal symmetric binary tree, verticalsymmetric binary tree, horizontal triple tree, and vertical triple tree;determine the partitioning for the coded video block based on thereceived signaling, wherein for a central node resulting from a tripletree partition, subsequent quadtree partitionings and a subsequentsymmetric binary tree partitioning which is parallel to the triple treepartition are disallowed; and reconstruct video data based on thedetermined partitioning for the coded video block.
 16. The device ofclaim 15, wherein the received signaling excludes bins indicatingpartitions that are not allowed.
 17. The device of claim 15, wherein thedevice includes a video decoder.